This video walks through the process of downloading and doing the initial configuration of WampServer, which is Apache, MySQL and PHP for Windows. It shows how to turn it on and off, as well as how to get files to show up from the localhost server.
Next up: WampServer Configuration.
If after installing WAMP you get a 404 error, make sure the server is actually running. Navigate to wampserver > apache > service > install service... opens prompt, hit enter... wampserver icon turns green.